1. Field of the Invention
The subject of the present invention is a dispensing assembly having a cylindrical container including a piston.
More particularly, the present invention relates to a dispensing assembly including a container and a dispensing member for dispensing the product contained in the container, the container being cylindrical and including a piston having a body made of rigid material having a cylindrical part carrying a seal made of elastic material.
2. Description of Related Art
In general, up to now, the piston includes a body made of rigid molded plastic, a part of which, of circular cross section, has, at the periphery, a lip molded as one piece with the body of the piston and located axially in the vicinity of a groove in which an O-ring seal is placed.
Such a piston has the drawbacks, on the one hand, of not providing foolproof sealing, by the construction, and, especially in the case where the product to be dispensed has a low viscosity and, on the other hand, of a high production cost, in particular when it is manufactured on a large scale, these drawbacks being explained in more detail in the description which follows. Especially when dispensing products liable to be degraded in contact with the ambient air, such as a hair dye, virtually perfect sealing is required, in particular in the case where this piston is propelled by a gas under pressure, such as compressed air.
Attempts have already been made to produce a piston seal economically. U.S. Pat. No. 4,027,810 describes a sealed cartridge plunger piston for grouting and caulking, the seal of which is arranged so as to provide perfect sealing throughout the duration of long storage of the cartridge, the products that it contains being sensitive to air and to moisture, and this is achieved taking into account the phenomena of thermal contraction and expansion. As a result, the seal is complicated to mold as are the anchoring means necessary for fastening the seal to the body of the plunger piston, and this seal in use serves only for the time to consume the product contained in the cartridge, the latter being subsequently thrown away. GB Reference No. 2,192,577 describes a gutter connector equipped with a seal; the connector and the seal are made of chemically compatible molded plastics making it possible, by the in-situ overmolding of the seal on the connector, to fasten the seal and to avoid having to provide means for holding the seal in place when fitting the gutter and, as a result, to decrease the fitting cost. It should be pointed out that, on the one hand, such a seal is a static seal and that, on the other hand, provision is made in the document to assist, if necessary, the fastening of the seal by a chemical route with a mechanical fastening, for example by molding dovetails.